Safety device for hand-controlled machines



July 3, 1956 SAIVES SAFETY DEVICE FOR HAND-CONTROLLED MACHINES Filed July 17. 1953 I LOAD 1 CIRCUIT United States Patent SAFETY DEVICE FOR HAND-CONTROLLED MACHINES Leon Saives, Billancourt, France, assignor to Regie Nationale des Usiues Renault, Billancourt, France Application July 17, 1953, Serial No. 368,757

Claims priority, application France August 5, 1952 1 Claim. (Cl. 317-135) This invention relates to safety devices in general and more particularly to a safety device applicable to any hand-controlled, electrically driven machine the operation of which is deemed dangerous during a predetermined portion of its cycle. The basic principle of the invention consists in providing two control members or pairs of interacting control memberspress-buttons, levers or the like-and circuit elements, the arrangement being such that the operator must press nearly simultaneously and with both hands on these control members for starting the machine.

In another co-pending patent application by same applicant, Serial No. 368,581 filed of even date, a safety device providing the same effect is described which operates through the medium of electronic circuit means.

This invention provides the same results but through electro-mechanical means instead of electronic circuit means.

As shown in the single figure of the aflixed drawing forming part of this specification, the safety device according to this invention comprises:

A transformer Tr having a plurality of input terminals whereby its primary 11 can be connected across any desired single-phase A. C. commercial network, the secondary 12 of this transformer being adapted to supply the transformed energy to the main locking and control elements of the device;

Two identical electrical circuits each comprising a pressbutton or control lever 1 or 4, in series with a relay R1 or R2 and normally closed contact F3 or F'3 respectively of a relay Ra.

An electrical circuit incorporating a pair of pressbuttons or control levers 2 and 3 connected in series with each other and with a pair of normally closed time contacts F1 and F2 the time-delay of which is adjustable within certain limits, and a pair of relays R3, R's; the relay Ra actuates instantaneously the normally closed contacts F F inserted in the other two circuits; the relay R'a controls the operative member or members of the machine. The relays R1 and R2, mentioned in the preceding paragraph, control the time contacts F1 and F2, respectively. The press-buttons 1 and 4 are operatively connected or coupled to the press-buttons 2 and 3, respectively.

Operation When the primary of the input transformer is energized, the apparatus is ready to operate.

As long as the operator does not actuate any of the control buttons at his or her disposal, the operative member or members of the machine remain unactuated since the double relay R3R3 is not energized.

If the operator depresses simultaneously with one hand the buttons 1 and 2, and with the other hand the buttons 3 and 4, both windings of relays R3, R are energized, thereby opening instantaneously the normally closed contacts F3, F's and neutralizing the relays R1 and R2, on the one hand, and closing the contacts disposed in the control circuit of the operative member or members of the machine, on the other hand.

If the operator depressed purposely or inadvertently a single set of press-buttons, for instance 1 and 2, the operative members of the machine cannot be started for a dual reason:

(a) The circuit of both relays R3 and R's remains open, because the button 2 has not been operated;

(b) After a predetermined, adjustable time period, the time-contact F1 controlled by the relay R1 now energized will re-open the circuit of relays R3 and R's. At this moment if the operator depresses the other set of pressbuttons 3 and 4, the relays R3 and R's will not be energized. The same will occur to the operative members of the machine.

To restore the apparatus to its operative condition, it will be necessary and sufficient for the operator to release both press-buttons 1 and 2, and the desired result will be obtained after but a few hundredths of a second.

Of course, the time-contacts F1 and F2 may be of any suitable type consistent with the purpose contemplated; they will be adjustable and adapted to provide a time lag of about two seconds, for instance.

Finally, as in the aforesaid co-pending patent application, it will be readily understood by anybody conversant with the art that the above-described arrangement is also applicable to machines the operation of which requires more than one operator.

I claim:

A safety device for hand-controlled machines performing an operation deemed dangerous to the operator which comprises a power supply, a first manual switch and a like second manual switch, each of said switches being independently operable and having two sets of normally open contacts interconnected such that activation of the one set activates the other set, a first time delay relay and a like second time delay relay, each of said relays having an operating coil and normally closed contacts, a third relay having two sets of normally closed contacts and a fourth relay having an operating coil and contacts controlling the operation of the machine, said switches and relays being connected in three parallel branches across said power supply, namely a first branch comprising one set of contacts of said first manual switch, the operating coil of said first time delay relay and one set of contacts of said third relay all connected in series, a second like branch comprising one set of contacts of said second manual switch, the operating coil of said second time delay relay and the other set of said contacts of said third relay all connected in series, and a third branch comprising the other set of contacts of said first and second manual switches, the operating coil of said third relay and the contacts of both of said time delay relays, all of said elements being connected in series, and the operating coil of said fourth relay connected in parallel with the operating coil of said third relay such that closing one of said other contacts by actuating only one of said manual switches will energize one of said time-delay relays and open its said normally closed contacts to open said third branch and maintain said fourth relay controlling said machine inoperative and closing both other contacts by actuating said manual switches simultaneously will energize said third and said fourth relay operating said machine and said third relay opening its said normally closed contacts to de-energize said first and second relays.

References Cited in the file of this patent UNITED STATES PATENTS 1,905,965 Leschke Apr. 25, 1933 2,301,491 Yanchenko Nov. 10, 1942 2,322,560 Beck June 22, 1943 2,579,595 McLane Dec. 25, 1951 

